String cannot be converted to ArrayList<String> Error

Question

Here is a program similar to the sinking battleship game from the book head first java. After compiling I am getting the error: "String cannot be converted to ArrayList Error" and ^ pointer point to the line I have two different files one with the main method and other a separate class. Whats wrong here.

Main method class

import java.util.Scanner;
public class SimpleDotComTestDrive{

   public static void main(String[] args){

      SimpleDotCom dot=new SimpleDotCom();
      boolean repeat=false;
      String[] locations={"2","3","4"};
      dot.setLocationCells(locations);   //^ where compiler points the error
      Scanner input=new Scanner(System.in);
      System.out.println("Lets Start");

      while(repeat==false) {
         System.out.println("Type your guess");
         String userGuess=input.nextLine();
         String result=dot.checkYourSelf(userGuess);
         System.out.println(result);

         if(result=="kill") {
            repeat=true;
            break;
         }
      }
   } //close main
} //close test class

Separately saved class which is part of this program:

import java.util.ArrayList;

public class SimpleDotCom {
   private ArrayList<String>locationCells;

   public void setLocationCells(ArrayList<String> locs) {
      locationCells=locs;
   }

   public String checkYourSelf(String userGuess) {
      String result="miss";
      int index = locationCells.indexOf(userGuess);
      if(index>=0) { 
         locationCells.remove(index);

         if(locationCells.isEmpty()) {
            result="kill";
         }
         else {
            result="hit";
         }
    }
    return result;
  } //close check yourself method
} //close simple class

setLocationCells takes an ArrayList but you are passing an array. — Arnaud Denoyelle
– Arnaud Denoyelle, Commented Mar 14, 2016 at 14:52
You are trying to set the List = "String" (or similar) while the "String" is not a List, so can not be assigned to it, only added to it as an element, using the .add("String") method — Stultuske
– Stultuske, Commented Mar 14, 2016 at 14:54

ninja.coder · Accepted Answer · 2016-03-14 14:55:04Z

2

You are getting the error because setLocationCells() method accepts an ArrayList<String> and you are passing it a String Array by doing:

dot.setLocationCells(locations);

You should either replace your method to accept String[] instead of ArrayList<String> or change your code as follows:

dot.setLocationCells(new ArrayList<String>(Arrays.asList(locations));

answered Mar 14, 2016 at 14:55

ninja.coder

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2 Comments

Andy Turner Over a year ago

You don't actually need the String - the type can be inferred by the diamond operator.

ninja.coder Over a year ago

@Andy Turner Yes, I agree. new ArrayList<>(...) will work. Thanks for pointing that out.

Nikolas · Accepted Answer · 2016-03-14 15:17:26Z

0

You cannot have String[] locations={"2","3","4"}; and then parse it to the method setLocationCells(ArrayList<String> locs){ that requires the ArrayList.

So, there are more ways:

Convert the array to list with: new ArrayList<String>(Arrays.asList(locations);

Define the ArrayList instead:

ArrayList<String> list = new ArrayList<String>() {{
    add("2");
    add("3");
    add("4");
}};

Change your method at all:

public void setLocationCells(String[] locs){
    Collections.addAll(locationcells, locs);
}

edited Mar 14, 2016 at 15:17

answered Mar 14, 2016 at 14:57

Nikolas

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3 Comments

Andy Turner Over a year ago

3. Not quite. Although the simple class name of the return value of Arrays.asList is ArrayList, it's actually java.util.Arrays.ArrayList rather than java.util.ArrayList. You'd need to copy it into a new ArrayList, as in 1.

Andy Turner Over a year ago

2. That's not valid Java.

Tom Over a year ago

I have tried change my method to: public void setLocationCells(String[] locs){ locationCells=Arrays.asList(locs); } but now getting cant find symbol ^Variable Arrays error

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